This invention is generally related to measuring the properties of electromagnetic′wave propagating through brain tissue, and assessing pathological statues of brain, and more specifically related to monitoring hydrocephalus, cerebral edema, and intracranial bleeding. The properties include and not limited to propagation time, travel velocity, complex wave number, phase shift, complex impedance and several parameters defined in this invention. Methods to minimize impacts of electrodes are proposed.
The condition known as hydrocephalus is described as the excessive build-up of the cerebrospinal fluid (CSF) in the brain cavities or ventricles. Under normal conditions, CSF is crucial to the functioning of the brain. It transports nutrients and wastes to and from the brain and creates a protective cushion of liquid. But an over-accumulation of CSF puts disproportionate pressure on the brain and can lead to brain cell and tissue damage. Thus, medical conditions that directly interrupt the regular flow and absorption of CSF into the bloodstream create the overabundance of CSF that ultimately leads to hydrocephalus.
Hydrocephalus has the potential of affecting people of all ages and can be categorized into two main groups: congenital hydrocephalus and acquired hydrocephalus. Congenital hydrocephalus is present at birth and can be the result of genetic abnormalities, prematurity, or influences during the fetal growth period. In contrast, acquired hydrocephalus develops over the course of a person's lifetime from the causes commonly, but not limited to, vascular disease, head injury or head trauma. Two sub-categories of hydrocephalus that primarily affect adults through strokes, hemorrhages, or head trauma are called hydrocephalus ex-vacuo and normal pressure hydrocephalus (NPH).
Although there isn't a national registry for citizens with hydrocephalus, there are some estimates to the significance of this condition within the nation's population. The National Institute of Neurological Disorders and Stroke branch of National Institute of Health estimates that about 1 in every 500 children are born with the condition. And recent statistics show that NPH is the origin of dementia in five percent of people over the age of 70 suffering from dementia.
When diagnosing hydrocephalus, most physicians utilize CT or MRI scans of the head. On the other hand, monitoring techniques currently consist mainly of invasive methods such as intracranial pressure monitoring, lumbar punctures (LP), or measuring CSF impedance using electrodes inserted in the CSF. In these procedures, a hole is required to assess the intracranial environment and sometimes LP can cause brain herniation & death. Recently, transcranial sonography (TCS) has been developed to noninvasively evaluate hydrocephalus, based on medical ultrasound technology. All of the above methods do not provide 24 hour bedside monitoring.
Another similar condition to hydrocephalus is cerebral edema. In response to brain injury such as trauma and infection, cerebral edema can result from the brain tissue swelling with excess water similar to how our ankles or knees swell after an injury. However, unlike our ankles or knees, our brain is surrounded by a thick and rigid skull that doesn't leave room for expansion and thus leads to an increase in intracranial pressure. If left unrecognized and untreated, cerebral edema can lead to permanent damage or death.
Another condition is intracranial bleeding due to head injury or trauma or surgery. The bleeding condition should be closely monitored to provide critical information for patient care.
It is desirable to have a method and a system of continuously monitoring hydrocephalus, cerebral edema, and cranial bleeding at a patient's bedside 24 hours a day in intensive care units. The system needs to be low cost and easy to use, and allows the automated monitoring and minimum intervention.